On Monday, Retrovirology published four papers about XMRV, a virus that has quickly become a celebrity for its putative association with chronic fatigue syndrome (CFS) and prostate cancer. The papers – and an accompanying overview – describe several lines of evidence that XMRV could be a laboratory contaminant. In other words, there might not be any such virus in the wild, let alone one that causes disease.

Now that's a contaminant. Image courtesy Flickr user frankenstoen.

Those findings alone would be enough to stir the ire of some CFS patients, but an accompanying press release put out by the Wellcome Trust to promote one of the papers went a step further, kicking off with this attention-grabbing lede:

A virus previously thought to be associated with chronic fatigue syndrome is not the cause of the disease, a detailed study has shown. The research shows that cell samples used in previous research were contaminated with the virus identified as XMRV and that XMRV is present in the mouse genome.

That story hit the wires immediately, and many news outlets reprinted it more or less verbatim. When reporters did bother to follow up with independent sources, they got virologists who had only had a short time to read the papers and think about them, leading to regrettable quotes like this.

As you’ve probably surmised by now, I’ve had the luxury of thinking about the work a bit longer, and don’t think these new papers settle the case. They do, however, raise a host of very significant questions about earlier XMRV research. They’re good science. Much of the earlier work on XMRV was also good science. The problem is that popular coverage of the whole field has left out most of the important caveats on both sides.

Blaming the media is too easy. Yes, they (okay, we) are part of the problem, but the scientists and patient advocacy groups are not guiltless. Ever since the Lombardi et al. paper appeared in Science last year, my TWiV co-hosts and I have been saying that the jury is still out about XMRV and CFS. It’s also still out about XMRV and prostate cancer, but that hasn’t gotten nearly as much hype.

Unfortunately, some researchers in the field haven’t been nearly as circumspect. Judy Mikovits, senior author on the Lombardi paper, has gone completely off the rails. Some of the authors on the new XMRV papers have also started playing fast and loose with the data. The Wellcome Trust’s press release, for example, quotes one of them:

“Our conclusion is quite simple: XMRV is not the cause of chronic fatigue syndrome,” says Professor Greg Towers, a Wellcome Trust Senior Research Fellow at University College London (UCL). “All our evidence shows that the sequences from the virus genome in cell culture have contaminated human chronic fatigue syndrome and prostate cancer samples.

“It is vital to understand that we are not saying chronic fatigue syndrome does not have a virus cause – we cannot answer that yet – but we know it is not this virus causing it.”

Towers’s peer-reviewed paper phrases it a bit differently, though:

Whilst our observations cannot conclusively prove that XMRV is not a human pathogen they appear consistent with the hypothesis that XMRV is not an exogenous virus transmitting among individuals.

I agree completely with peer-reviewed Towers, but think press-release Towers needs to calm down a bit.